Sound box for talking machines



March 30 1926. 1,578,285 M. A. HARDYMAN SOUND B oxIFoR TALKING MACHINESFiled April 11. 1922 f Ma Patented Mar. 30, 1 926. g

UNITED STATES I "1,578,285 PATENT OFFICE;

MAURICE.ARTI-IURHARDYMAN, OF CHARLTON, LONDON, ENGLAND, ASSIGNOR TO JOHNHARLINGBAILEY, OF LONDON, 'ENGLANDQ SOUND BOX FOB TALKING MACHINES.

Application filed April 11,1922. Serial No. 551,653.

To all whom it may concern. v

Be it known that I, MAURICE ART UR HARDYMAN, a subject of the King ofEngland, residing at Charlton, London, England, haveinvented certain newand useful Improvements in Sound Boxes for Talking Machines, of whichthe following is a specification. 1

This invention is for improvements in or- According to this invention,such a soundbox is provided with a sound-chamber. be-

-' tween the back-plate and the tone arm socket, said chamber being of adiameter approximately equal to that of the operative portion of thediaphragm and, preferably, in-depth considerably deeper than the spacebetween the back-plate and the diaphragm. The presence of-this chamberis found to result in a fuller tone which may be still further mellowedby constructing the chamber of non-resonant material, such, for example,as woo The front plate of the sound-box having a sound-chamber asdescribed above, may have a small central perforation of diameter onlysuch as is sufficient for the entrance and operation therein of thestylus-lever, instead of V the usual large opening, for the purposeofscreening the diaphragm from external noises, such as arise from thescratching of the stylus upon the gramophone record.

In the accompanying drawings:

Figure 1 is a central vertical section through the sound-box atright-angles to the plane of the diaphragm;

Figure 2 is a plan of a diaphragm having a circular corrugation, and VFigure 3 is a section through the diaphragm shown in Figure 2 on theline 3-3 of that Figure. V

A diaphragm A is mounted between a back-plate B and cover-plate Thecover plate C is cup-shaped and accommodates within it the diaphragm Aand two spacing rings D. The back-plate-B provides a foun-f datlon uponwhich the diaphragm, sand-- wiched at itsiperiphery between the spacingrings D, is clamped by the plate C.

'hfounted on the back of the plate B concentrically with the diaphragmis a circular chambered member E of wood disposed with its open endtowards the plate B. The other end of this chambered member is formedwith a short tubular extension E in which is a tone-arm socket F. i Thesocket F has a circumferential flange F on its inner end which engagesthe inner face of the outer end of the chambered member E and throughwhich it is screwed to said outer end. The internal diameter of thechambered member E is approximately equal to the diameter of theoperative portion of the diaphragm A, and the interior depthfrom theback plate Bis approximately three times the depth of the space betweenthe diaphragm and the back-plate. The back plate B has in it the usualcentral perforation B of diameter nearly equal tothat of the through-wayof the tone-arm socket F,

The plate G'has a small central perforation 0 through which a styluslever G opcrates; otherwise the plate C is imperforate. 1

The styluslever is mounted in the usual way on the exterior of thesound-box and is attached to the centre of the diaphragm.

In a preferred form of sound-box the diaphragm A is made of somemouldable' material such as sheet ebonite instead of the usual micadisc, and is formed'with one or more circular corrugations A as shown inFigures 2 and J f The ebonite may be of the class usually employed forelectrical purposes and is preferably about 1/64th of an inch thick.

The corrugation A *is centrally disposed and lies near the periphery ofthe diaphragm but clearof. the spacing rings sound-box, so that it mayflex freely with the operative portion of the diaphragm,

v The corrugation may be formed by ress-' ing the ebonite disc into amould while 'ot.

By the employment of such a diaphragm, the tone is much improvedcompared'with that when the usualmica disc is used.

I claim 1. In a talking-machine sound-box, the

D when the diaphragm is in place in the combination of a diaphragm,aback-plate behindthe diaphragm having in itan opening for passage ofsound emanating from the diaphragm, a tubular tone-arm socket Whosesound inlet is disposed opposite the opening in the back-plate, and ahollow cavity member of wood interposed between the back-plate end thetone-arm socket so asto provide a sound cavity behind the backplate andbetween it and the tonearm socket inlet, .the interior of which cavityinei'nber is so dimensioned that the cavity is greater in diain-eter'than the opening in; the

"back-plate andthe inlet of the tone-arm socket and v greater indepththan the space behind the diaphragm having in it anopening for passageof sound emanating from the diaphragm, a tubular tone-arm socket Whosesound inlet is disposed opposite the opening in the back-plate, and 'ahollow cavity-member of woodinterposed between the backplate and thetone-arm socket so as to provide a sound cavity behind'the backplateand: between it and the tone-arm socket-inlet, the interior of whichcavity member is so dimensioned that the cavity is substantially equalin diameter to the operative portion of the diaphragniand substantiallyequalin depth to three times the depth "of the space between the d-i-a e'e i and thetaek-plate, substantially: described In. testimony whereof Ialiix my signature.

MAURICE ARTHUR HARDYMIAN

